Effect of auxiliary preheating of filler wire on dilution in gas metal arc stainless steel surfacing using RSM

Abstract

Weld surfacing is a process for producing surfaces with good corrosion resistant properties by means of depositing/laying of stainless steels on low carbon steel components with an objective of achieving maximum economy and enhanced life. The aim of the work presented here was to investigate the effect of auxiliary preheating of the solid filler wire in mechanised gas metal arc welding (GMAW) process (using a specially designed torch to preheat the filler wire independently, before its emergence from the torch) on dilution. Four factor five level central composite rotatable design was used to develop relationship for predicting dilution, which enables to quantify the direct and interactive effects of four numeric factors, namely, wire feed rate, arc voltage, welding speed and electrode extension, and one categorical factor, preheat current. Mathematical models developed show that dilution increases with increasing wire feed rate, arc voltage and welding speed, whereas it decreases with increasing electrode extension and preheat current. External preheating of the filler wire resulted in greater contribution of arc energy by resistive heating due to which significant drop in the main welding current values and hence low dilution levels were observed. Numerical optimisation was carried out and the optimal solutions generated indicate that for same levels of dilution, higher deposition rates are achievable in the auxiliary preheating arrangement. Conformity experimental runs show a good agreement with the numerical results.